1. Field of the Invention
The present invention generally relates to semiconductor device substrates and, more particularly, to a semiconductor device substrate using a silicon substrate having fine wires formed thereon and a manufacturing method thereof.
2. Description of the Related Art
With high densification of semiconductor devices, the pitch of mounting terminals of semiconductor devices has become smaller. However, since the connection-terminal pad of a circuit board on which a semiconductor device is mounted is formed with a pitch larger than the pitch of the mounting terminals of the semiconductor device, it is difficult to mount the semiconductor device as it is.
Thus, the semiconductor device is mounted on a substrate, which is referred to as an interposer, so as to mount the semiconductor device on a circuit board via the interposer. That is, the electrodes of the semiconductor device are rearranged by the interposer so as to form mounting terminals having a larger pitch, thereby matching with the pitch of the connection-terminal pads on the circuit board.
Generally, the above-mentioned semiconductor device substrate (interposer) has a multilayer structure in which conductive members extend from a surface on which a semiconductor device is mounted to an opposite surface on which mounting terminals are formed. Generally, an organic fine substrate is used for the interposer. In order to obtain finer wiring pattern, a silicon substrate is used in many cases. A multilayer structure is formed by stacking insulating layers and conductive layers on a silicon substrate. The conductive member that penetrates an insulating layer can be easily formed by a through hole such as a plated via hole of a build-up substrate. A silicon substrate has a relatively large thickness so as to maintain a strength as an interposer. Therefore, a special fabrication process is needed so as to form the conductive members that extend in a direction of the thickness with a fine pitch.
An approach as one method of forming the conductive member that extends through a silicon substrate will be explained below.
First, a thick silicon substrate is prepared, and holes having a thin cylindrical shape are formed in the silicon substrate in the same arrangement as mounting terminals. Each hole having the thin cylindrical shape is referred to as a blind via that extends to the middle of a silicon substrate. After forming an insulating film on an inner surface of each hole, a metal is filled in each hole by electro-plating or filling a metal paste. The filled metal finally becomes the conductive members that penetrate the silicon substrate, and ends thereof serve as mounting terminals to be connected to the circuit board.
A wiring layer is formed on the top surface of the silicon substrate after filling the metal in the holes. The conductive members in the holes of the silicon substrate and the electrode pads formed on the top surface of the wiring layer are electrically connected to each other through via holes or the like. The electrodes of the semiconductor device will be connected to the electrode pads.
After the wiring layer is formed on the top surface of the silicon substrate, ends of the conductive members in the holes of the silicon substrate are exposed by grinding (back-grinding) or etching the back surface of the silicon substrate. The back surface of the silicon substrate may be grinded until the ends of the conductive members in the holes of the silicon surface are grinded, and, thereafter, the ends of the conductive members are protruded by selectively etching only the silicon substrate. The thus-formed protruding ends serves as mounting terminals, and, thus, the semiconductor device mounted on the semiconductor device substrate (interposer) can be flip-chip mounted on the circuit board.
With the above-mentioned fabricating method of the interposer, it is necessary to form a plurality of deep cylindrical holes in a silicon substrate that are arranged in parallel with a small pitch. In order to form such deep holes in a silicon substrate, it is necessary to use a special dry etching method such as reactive ion etching (ICP-RIE). The reactive ion etching is not used in the usual semiconductor device production process (a process for fabricating a mounting substrates such as an interposer), and needs special and expensive apparatuses and processes. Therefore, the manufacturing cost of the semiconductor device substrate (interposer) will increase.
Moreover, the above-mentioned method needs the process for filling a metal in the deep holes in the silicon substrate. However, it is difficult to fill a metal in a deep hole without an air gap or an empty space, and a long process time is needed to fill a metal by plating.
It is a general object of the present invention to provide an improved and useful semiconductor device substrate in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide a semiconductor device substrate having fine terminals with a small pitch and is able to be easily produced at a low cost without using a special process.
In order to achieve the above-mentioned object, there is provided according to one aspect of the present invention a semiconductor device substrate comprising: a silicon substrate having a first surface and a second surface opposite to the first surface; at least one mounting terminal having a pyramidal shape and extending between the first and second surfaces, an end of the mounting terminal protruding from one of the first and second surfaces; and a wiring layer formed on the first surface of the silicon substrate, the wiring layer including a conductive layer that is electrically connected to the mounting terminal.
According to the above-mentioned invention, the mounting terminal having a pyramidal shape can be easily formed by using the recess formed in the silicon substrate since such a recess having a pyramidal shape can be easily formed in the silicon substrate by etching which does not require special processing apparatuses. Additionally, since mounting terminal has a top of the pyramidal shape, the top end of the mounting terminal can be stuck into a member to which the mounting terminal is connected, thereby achieving a good electrical contact.
In the semiconductor device substrate according to the present invention, an insulating film formed of a silicon oxide film may be interposed between the mounting terminal and the silicon substrate. Additionally, the first surface of the silicon substrate may be covered by an insulating layer formed of an organic insulating film. Further, the second surface of the silicon substrate may be covered by an insulating layer formed of an organic insulating film. The wiring layer may have a multiplayer structure in which insulating layers and conductive layers are alternatively stacked.
In the semiconductor device substrate according to the present invention, the pyramidal shape of the mounting terminal may be defined by crystal planes of the silicon substrate. The first and second surfaces of the silicon substrate may be substantially parallel to the (001) plane of silicon crystal. The mounting terminal may have a hollow pyramidal shape. A top end of the mounting terminal may protrude from the second surface of the silicon substrate.
Additionally, there is provided according to another aspect of the present invention a method of manufacturing a semiconductor device substrate, comprising the steps of: forming a recess of a pyramidal shape in a first surface of a silicon substrate; forming an insulating film on the first surface of the silicon substrate and an inner surface of the recess; forming a conductive layer in the recess, the conductive layer being configured and arranged to be a mounting terminal; forming a wiring layer on the first surface of the silicon substrate, the wiring layer including a conductive layer electrically connected to the conductive layer in the recess; and removing the silicon substrate from a second surface opposite to the first surface of the silicon substrate so as to have the conductive layer within the recess exposed in a protruding state.
According to the above-mentioned method, the mounting terminal having a pyramidal shape can be easily formed by using the recess formed in the silicon substrate since such a recess having a pyramidal shape can be easily formed in the silicon substrate by etching which does not require special processing apparatuses. Additionally, since mounting terminal has a top of the pyramidal shape, the top end of the mounting terminal can be struck into a member to which the mounting terminal is connected, thereby achieving a good electrical contact.
In the method according to the present invention, the step of forming the recess may include a step of removing a predetermined part of the silicon substrate in a pyramidal shape by etching. The method according to the present invention may further includes a step of forming an insulating film on a second surface of the silicon substrate opposite to the first surface after the step of removing the silicon substrate.
The step of forming the insulating film on the second surface may include a step of forming a silicon oxide film on the second surface. Alternatively, the step of forming the insulating film on the second surface may include a step of forming an organic insulating film on the second surface. The step of removing may include: a first step of grinding the second surface of the silicon substrate; and a second step of removing the silicon substrate by etching after the first step so as to have an end of the mounting terminal protrude from the etched surface.
Additionally, there is provided according to another aspect of the present invention a semiconductor package comprising: a semiconductor device substrate; and a semiconductor element having at least one metal bump formed on an electrode pad thereof, wherein the semiconductor device substrate comprising: a silicon substrate having a first surface and a second surface opposite to the first surface; at least one mounting terminal having a pyramidal shape and extending between the first and second surfaces, an end of the mounting terminal protruding from one of the first and second surfaces; and a wiring layer formed on the first surface of the silicon substrate, the wiring layer including a conductive layer that is electrically connected to the mounting terminal, and wherein an end of the mounting terminal of the semiconductor device substrate is connected to the metal bump in a state where the end of the mounting terminal protrudes into the metal bump. Accordingly, a good electrical connection can be achieved between the semiconductor element and the semiconductor device substrate.
Additionally, there is provided according to another aspect of the present invention a semiconductor package comprising: a semiconductor device substrate; and a semiconductor element having at least one metal bump formed on an electrode pad thereof, wherein the semiconductor device substrate comprising: a silicon substrate having a first surface and a second surface opposite to the first surface; at least one mounting terminal having a pyramidal shape and extending between the first and second surfaces, an end of the mounting terminal protruding from one of the first and second surfaces; and a wiring layer formed on the first surface of the silicon substrate, the wiring layer including a conductive layer that is electrically connected to the mounting terminal, and wherein the semiconductor element is mounted on the wiring layer of the semiconductor device substrate, and the mounting terminal of a pyramidal shape is used as an external connection terminal. Accordingly, the external connection terminal of the semiconductor package becomes a pyramidal shape, which provides a good electrical connection when the semiconductor package is connected to a circuit board.
Additionally, there is provided according to another aspect of the present invention a semiconductor package comprising: a semiconductor element; a semiconductor device substrate having a first surface and a second surface opposite to the first surface, the semiconductor element being mounted on the first surface; and a package substrate facing the second surface of the semiconductor device substrate and electrically connected to the semiconductor element via the semiconductor device substrate, wherein the semiconductor device substrate comprising: a silicon substrate having the first surface and the second surface opposite to the first surface; at least one mounting terminal having a pyramidal shape and extending between the first and second surfaces, an end of the mounting terminal protruding from one of the first and second surfaces; and a wiring layer formed on the first surface of the silicon substrate, the wiring layer including a conductive layer that is electrically connected to the mounting terminal. Since the semiconductor device substrate can be formed in a fine structure, the semiconductor element having a fine structure can be mounted on the package substrate without forming the package substrate in a fine structure.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.